Industrial gas emissions of carbon dioxide (CO₂) and methane contribute to the Greenhouse Effect, whilst gases containing halogens, such as sulphur hexafluoride (SF₆), banned from use, except in electrical switchgear, are far more damaging greenhouse gases, but have lower concentrations in the atmosphere. It has been estimated that mitigating climate change will cost the EU 4 % of GDP by 2100.

Sensitive instruments are used to monitor trends in greenhouse gas concentrations and to identify sources of halogenated emissions. These rely on extremely low level and very specific gas calibration standards to confirm their performance. Increasing the accuracy of atmospheric monitoring, and identifying gas emission sources, relies on the production of reference gas standards or complex halogenated gas mixtures with robust links to SI units.

This project developed SI-traceable gas cylinder standards and point-of-use reference gas standards, including CO₂ standards isotopically matched to the ratio of ¹³CO₂ to ¹²CO₂ in the atmosphere.

The Project:

• Developed synthetic “zero” air gas standards with quantified amounts of the traces of gases to be measured. These are used in the production of reference gas standards and for setting instrument background responses
• Developed stable gas cylinder based and point-of-use reference gas standards for CO₂, CO, N₂0, and halogenated gases to enable low uncertainty instrument calibration at the levels present in the atmosphere
• Developed an optical transfer standard based on spectral line data with traceability to the SI for characterising laser-based spectroscopic instrumentation that is used for atmospheric measurements of CO and CO₂
• Evaluated the use of Optical Isotopic Ratio Spectroscopy for determining the effects of different isotope abundance in analysis samples. This is important for increasing the accuracy of calibration standards and determining the sources of greenhouse gases.

This project has successfully developed a range of traceable reference gas and optical transfer standards for the improved calibration of greenhouse gas-monitoring instrumentation. Newly developed standards, for example, have significantly improved the accuracy of atmospheric CO₂ measurements made by the UK’s national and international greenhouse gas-monitoring networks. Trace level reference gas standards containing complex mixtures of fluorinated gases have been used in system testing at the EMPA Dübendorf monitoring site (Switzerland) introducing robust traceability to the SI for their measurements. Project results will help climate-monitoring networks to achieve the target measurement accuracies set by the WMO as well as supporting the implementation of industrial emissions regulations and directives, including the EU’s F-gas legislation and air quality directive (2008/50/EC).